Posted
by
Soulskillon Friday November 30, 2012 @04:30PM
from the fat-guy-little-coat dept.

An anonymous reader sent word that astronomers have discovered an absolutely enormous black hole residing in a galaxy that seems too small for it. In a new study (PDF), researchers looked at galaxy NGC 1277 and found that its central black hole weighed in at roughly 17 billion solar masses. Quoting Phil Plait: "The problem is, that’s far more massive than the central bulge of NGC 1277 would suggest the black hole should be. It’s well over half the total mass of the bulge! In fact, the entire mass of the galaxy is about 120 billion solar masses, which means the black hole at its heart is 14 percent of the total galaxy’s mass; compare that to the Milky Way’s black hole mass of 0.01 percent and you’ll see why astronomers were shocked."

This is just an example of a MaCHO [wikipedia.org]. We've theorized about them for a while. They are a strong candidate for a bulk of the dark matter we've detected. The other candidates are WIMPs [wikipedia.org].

Well yes if you use the size of the event horizon and the mass of the black hole to calculate density then you get a low density.

But the mass is not distributed over that volume. inside the black hole the mass is actually contained in an infintesimal point, and the density is infinite. At least according to the math; it's impossible to look inside the event horizon to find out if that's really the case.

At the very least it's clear that a black hole must have density significantly higher than that of a neutron star. Saying it's less dense than the air is misleading in that respect.